The Tax Office has put the nation’s wealthiest families on notice that it is watching closely for any restructuring of their assets or specious strategies to avoid Labor’s proposed tax on superannuation balances above $3 million.

The new tax is not yet law but the ATO has quietly added it to its priority list for wealthy private groups. A spokesman said the Tax Office wanted to understand the “behavioural responses” to the planned tax that might already be occurring.